Directional indicating instrument



Oct. 20, 1953 J. c. HEwlTT, JR

DIRECTIONAL INDICATING INSTRUMENT Filed May s. 1949 rroQ/VEY.

Patented Oct. 20, 1953 UNITED STATES ATENT OFFICE DIRECTIONAL INDICATINGINSTRUMENT John C. Hewitt, Jr., Long Beach, Calif.

Application M'ay 9, 1949, Serial No. 92,233

9' Claims'. l

This invention relates generally to improvements in directionalindicating or recording instruments employing a magnetic compass. fromthe position of which, asin rel-'ation to a reference object, may beobtained a. directional, or azimuthal determination. The invention isdirected particularly' to certain important. ad'- vances in wellsurveying instruments used for such purposes; as the orientation of theinstrument in the well, orientational location of an object. extraneous:to the instrument, or orienta- .tion of' the wellcourse itself, As anillustrative adaptation, the invention will be described as embodied inaV well surveying instrument operableto produce a photographic record ofa contained compass element.

It has been conventional practice to use: this type of instrumentI fordetermination oi the azimuthal location in the Well of a. magnetic. ob-

' ally attracted one by the other.y

ject, such as the drill pipe or tool within which f the instrument islowered, or such other specific bodiesv as a metallic lishv ormagnetized marker or' reference insert. carried byI the objectto. hesurveyed. The general method employed' is to lower the instrument to adepth bringing its compass: opposite the magneticbody and thenphotographing orV otherwise recording the compass position, all with thesupposition that. the compass accurately points toward and thereforeindicates the location of the magnetic obieet.

Practical operations have demonstrated however, that the'- eompassposition recording does not in' all instances give a true directionalindication of' the object being' surveyed. Error may arise for any ofvarious reasons. As an example, assume the purpose of the survey to bethat of directionallylocating a fish lodged ata location inthe side ofthe well coincident with a Well bore diameter aligned with the earthsmagnetic poles. Since the instrument compass normally alines itself`with respect tothe earths: magnetic iield', that alimement might not.appreciablyt be affected with the, compass; lowered oppositethe fish,and consequently a record taken at that depth would noty itselfimlicate.1 whether at the time of recording, the instrument had beenlowered toA proper position, or had been lowered to some differentlocation. sul-iiciently remote from, the fish as to bef unaffected byits mag,- neticl properties. To cite another example, where the,instrument. is used to. determine the orienta,- tion of a magnetizedinsert in, one side off a tool or drill string, through inaccurate.operations the Vinstrument may not have been lowered to the proper depthopposite the insert', at the time when the record is taken. The resultmay be 2. an assumed, but erroneous, reading since the recorded image ofthe compass does not' itself show Whether the proper recording positionhad been reached by the instrument.

My primary obi-ect is to provide an improved direction findinginstrument capable of producing: av record which itself: distinguishesbetween a recording of the earths' polarity, as compared with theazimuthal position of a magnetized obf ject in the Well. Pursuant to theinvention, I

employ a pair of compass elements mounted preferably in tandemarrangement for rotation about a common axis, and in sufciently closeproximity that the compass elements are mutu- Specincally, their mutualmagneticY attraction is such that normally, that is' when inuenced-onlyby the earths magnetic: field, they assume opposite polarity, the southpole. of one element; being brought opposite and in substantialalinement with the north pole of the other element.Y To effect suchrelation, one of. the compass: elements may be more strongly magnetizedso as normally to govern the. position, of a second and less stronglylmagneti-Zed element, the latter' thus becoming a tell-tale?m which showsby its variances from the: stated normal relation of the. elements, the,presence of a magnetic influence other than the earths magneticattraction As will appear,

' suitable provision maybe made for recording the relative: positionsof. the; compass' elements, as for: example an appropriate light sourceand recording nlm; arrangement.

Front. the foregoing it will bee understood' that While the instrumentinitially is being lowered the, weil withthe compass elements solelyunder the; influence oi the earths magnetic field, thefelements Willremain in aligned opposite polar relation, and that a record taken,under such conditions. will indicate the absence of magnetic: influence;other than that of the. earths field. When. however, the. instrinnentvis brought opposite.` a magnetic body, the. resulting attraction tendsto bring` the more, strongly magnetized.' elementinto directionalalinement. with that. body, While at the. ysame time causing, thetell-tale element, tol deflect fromv its normal position ofali'nernentvvith` the primary compass, to a degree,v dependent upon thestrength. of.' the extraneous magnetic attraction. Where. the externalobject' is. strongly' magnetic, the relative positions oi the CompassesWillbe complete-ly reversed',` bringing their poles into correspondence,Whereas in` other.e instances, thev relative deflec- In eitherinstance,the recorded positions of the `3 compass elements show denitely thepresence of the extraneous magnetic object and its direction.

rShese various objects of the invention, as well as the details of atypical and illustrative embodiment, will be explained to betteradvantage in the following more detailed description of the accompanyingdrawing, in which:

Fig. 1 is a sectional view showing the instrument lowered typically in apipe string to be oriented, and with the instrument away frompredetermined recording position thereon;

Fig. 2 is a fragmentary View showing the compass needle assembly inrecording position as infiuenced by a magetized element carred by thepipe string;

Fig. 3 is a view taken from line 3-3 of Fig. l vand illustrating therelative positions of the compass elements; and

Fig. Li shows a typical inclination and azimuth recording taken on thelight sensitive recording element.

Referring rst to Fig. 1, the recording instrument is shown to comprise asuitable housing illustrated typically as a cylindrical non-magneticcase I containing a light source I I, compass needle assembly I2, lightdirecting lens means I3, an inclination indicator I4 and an appropriaterecording means I5. While it is understood that the invention andinstrument are adaptable for running well surveys for various differentpurposes and under conditions varying accordingly, as a typicaladaptation I have shown the instrument to be run down in a pipe stringII whose orientation and inclination are to be determined at apredetermined depth, the illustrated section of the string beingmagnetic or non-magnetic and carrying a strongly magnetized element orinsert conventionally indicated at I1, or a pair of diametricallyopposed magnetized inserts Il and IB.

The invention is concerned primarily with the compass assembly I2 andits structural and functional relationships to other parts of theinstrument and the operating environment, all as will later appear. Inthe illustrative form shown, the compass elements proper are mounted ina suitable container I9 inserted and held in fixed position within theinstrument case I0, the container I9 having translucent or transparenttop and bottom ends 2B and 2|. Shaft 22, supported and iournaled forrotation in the container walls 2G and 2|, carries a primary compasselement 23 shown specifically in the form of a transparent ortranslucent disc 24 xed to the shaft 22 and carrying the radial azimuthor angularity markings 25, see Fig. 3. The disc carries also a polarmagnetized compass element which may be of the known segmental ring type26 contained within a peripheral groove 21 in the disc, the north poleof the needle being suitably indicated as by the circle at N, and thediametrically opposed south pole by the marking at S. Shaft 22 supportsa second compass element, which may serve essentially as a tell taleneedle 28 carried by sleeve 2i! rotatable about :and relative to theshaft. Thus the two compass elements are mounted for independent andrelative rotation.

In the illustrated assembly, the two compass elements are mountedaxially in tandem arrangement and in such close proximity as to bemutually attracted each by the other, such attraction being suicientlystrong that when iniiuenced only by the earths magnetic eld the northand Vsouth poles of the tell tale neede 28 are attracted respectively tothe south and north poles of the primary compass element 23, with thepoles of both Compasses in substantially the same plane. Preferably theprimary compass 23 will be relatively strongly magnetized and thereforemay be said to be primarily controlling as to the directional indicationgiven by the assembly. Being less strongly magnetized, the tell talecompass 28 normally or under the influence of a relatively Weak magneticattraction, such as the earths magnetic field, is controlled by theprimary element 24 to the extent of assuming an opposite polar position,as described. The polarity of the needle 28 may be suitablydistinguished, as by giving its north pole the enlarged form indicatedat 3U.

When used in a recording instrument, the compass assembly I2 may bepositioned below the light source I I, shown typically to comprise anelectric lamp 3l energized by batteries 32 under suitable control, notshown. Light from the ylamp passes through the translucent walls 2G and2|, and also through the primary compass disc 24 to the lens 33 fromwhich the light is projected past the inclination indicator I4 to alight sensitive or photographic iilm 3a. The inclination indicator isshown typically to comprise a plumb bob 35 suspended from thetranslucent support 3E and carrying a reticule with the cross hairs 3l.As soon will be understood, the record taken on the film 34 willcomprise the combined or superimposed images of the cross hairs 31,needle 28, and the angular markings and polar indicia of the primarycompass 2li.

In considering the operation of the instrument, assume rst the compassassembly to be lowered to a depth at which it is subjected only to theearths magnetic influence. Under such conditions the two compasselements will lassume the relationship illustrated in Fig. 1, and theirpositions if recorded on the nlm 34 would appear to have therelationship illustrated in Fig. 3. It is important to observe that theresulting record would itself indicate the absence of any strongextraneous magnetic attraction. Should the compass needle assembly belowered opposite a magnetic body such as a :ish oiset in the well, thepresence and angular location of such attraction may be indicatednotwithstanding the fact that its magnetic attraction may beinsuflicient to reverse the relative positions of the Compasses. Thepresence of such attraction may deflect the tell tail needle 28 frompolar alinement with the primary compass, because of the tendency forthe corresponding poles of both Compasses to aline with or point in thedirection of the attraction. Thus while the angular position of themagnetic attraction will be indicated with substantial accuracy by theprimary compass'deection of the tell-tail needle from its Fig, l, Fig. 3position (though the deflection is less than complete reversal) Willindicate and any record taken 'at such time will show, that the compassassembly position is influenced by an attraction other or greater thanthat of the eaths magnetic force.

Assume now the compass assembly to be lowered opposite the stronglymagnetized element or elements Il, I8, as in Fig. 2. Here the extraneousmagnetic attraction is suiiiciently great to overcome the mutualattraction of the Compasses to the extent of causing complete polarreversal of the tell-tale needle. Accordingly, a record taken will showthe compass elements as illustrated in Fig. 4, where the corresponding.poles accesos appear in adjacent relation and all the poles in linearalinement. Assuming the instrument, or tubingI it to beinclined, therecord' showv also the offset position of the reticule and cross hairsal.. Accordingly, from the composite record may be' determined both'thev mrientation.v oi the. tubing and the direction of its inclmation,

IEA claim:

1. A directional indicating instrument tor use in wells, comprising' ahousing, a. pair of magnetic compasselementsmounted for rotation about acommon vertical axis in the housing and having north and south poies insuch proximate relation that the elements are mutually attractive, said`elements being of such` magnetic strengths andV so relatively positionedthat when subjected toonly the earths magnetic field one of saidelements maintains the other in a. position substantially completelyreversed from that of the one element and from the position which saidother element would assume in the absence of said mutual attraction,Asaid housing being adapted to be lowered in a well to bring saidelements opposite a magnetic material, the elements being of suchmagnetic strengths ,and so relativelyv positioned as to then beattractable to said material in substantially correspondingV vpolarrelation in which vthe relative positions of the elements are reversedfrom their positions assumed rwhen subjected only to the earths magneticfield, and means for indicating the relative positions of said elementsas between their positions when subjected only to the earths field andtheir positions in said corresponding polar relation.

2. A directional indicating instrument for use in Wellsz comprising ahousing, a pair of magnetic compass elements mounted for rotation abouta common vertical axis in the housing and. having north and south poles.in such proximate relation that the elements are mutually attractive,one. of said elements being magnetized suciently more strongly than theother that. when subjected to only the earths magnetic field said oneelement maintains the other in a position substantially completelyreversed froml that of the one element and from the position which saidother element Would assume in the absence of said mutual attraction,said housing being adapted to be lowered in a Well to bring saidelements opposite a. magnetic material, the elements being of suchmagnetic strengths and so relatively positioned as tothen be attractableto said material in substantially corresponding polar relation in whichthe relativev positions of the elements are reversed from theirpositions assumed when subjected only to the earths magnetic field, andmeans in said housing for recording the relative positions of saidelements.

3. A directional indicating instrument for use in wells, comprising ahousing, a pair of magnetic compass elements mounted for rotation abouta common vertical axis in the housing and hPa-ving north and south polesin such proximate relation that the elements are mutually attractive,one oi said elements being magnetized suinciently more strongly than theother that when subjected to only the earths magnetic iield said oneelement maintains the other in a position substantially completelyreversed from that of the one element and from the position which saidother element would assume in the absence of said mutual attraction, avertical shaft carry- 'ing one of said elements, the other element beingsupported by and rotatable about said shaft,

.6 said housing; being'adapted to.v be lowered in a` weil to bring saidelements opposite a magnetic material, the elements' being of. suchmagnetic strengthsI and so relatively positioned as to. then beattractable to said material in substantially corresponding polarrelation inwhic-h the relative positions oi the: elements are reversedfrom their positions. assumed when subjected: only to the earthsmagnetic' eld, and means in said housing for recording the relativepositions of said elements;

4i a directional indicating instrument, the combination comprising apair.v of magnetic com.- pass elements each having north and south mag.-netic poles mounted in such proximate relation that the elements; aremutually attractive, said elements being of such. magnetic strengths andso relatively positioned. that when subjected to the earths magneticfield one oi said elements maintains the other in a positionsubstantially oompletehz' reversed from that of the one element and'from the. position which said other element would assume. in the absenceof said mutual attraction, and said elements; being of such magneticstrengths and so relatively positioned. as to be relatively deflectibleby' a magnetic material inthe vicinity of the instrument, saidinstrument including means. for indicating the relative positions ofsaid elements.

5. In a directional indicating instrument, the combination comprising a,pair of magnetic compass elements each having north and south magneticpoles mounted in. s-uch proximate relation that the elements aremutually attractive, said elements being of such magnetic strengths andso relatively positioned that when subjected to the. earths magneticfield one ofsaid elements maintains the. other in. a positionsubstantially ycompletely reversed from that ci the one element andfrom. the position which said other element would assume in the absenceof said mutual attraction, and said elements. being oi' such magneticstrengthsv and so. relatively positioned as to be attractable toamagnetic material in the: vicinity of the instrument in substantiallycorresponding polar relation in which the relative positions of theelements are reversed from .their positions assumed when subjected toonly the earths magnetic eld, said instrument including means forindicating the relative positions of said elements as between theirpositions when subjected only to the earths eld and their positions insaid corresponding polar relation.

6. In a directional indicating instrument, the combination comprising apair of magnetic compass elements mounted for rotation about a commonvertical axis and having north and south magnetic poles in suchproximate relation that the elements are mutually attractive, one ofsaid elements being magnetized sufficiently more strongly than the otherthat when subjected to only the earths magnetic iield said one elementmaintains the other in a position substantially completely reversed fromthat of the one element and from the position which said other elementWould-assume in the absence of said mutual attraction, said elementsbeing of such magnetic strengths and so relatively positioned as to beattractable to a magnetic material in the vicinity of the instrument insubstantially corresponding polar relation in which the relativepositions of the elements are reversed from their positions assumed whensubjected only to the earths magnetic eld, said instruments includingmeans for indicating the relative positions of said elements as betweentheir positions when subjected only to the earths field and theirpcsitions'in said corresponding polar relation.

7. In a directional indicating instrument, the combination comprising apair of magnetic compass elements mounted for rotation about a commonvertical axis and having north and south magnetic poles in suchproximate relation that the elements are mutually attractive, one ofsaid elements being magnetized suiiciently more strongly than the otherthat When subjected to only the earths magnetic field said one elementmaintains the other in a position substantially completely reversed fromthat of the one element and from the position which said other elementwould assume in the absence of said mutual attraction, said elementsbeing of such magnetic strengths and so relatively positioned as to thenbe attractable to said material in the vicinity of the instrument insubstantially corresponding polar relation in which the relativepositions of the elements are reversed from their positions assumed whensubjected only to the earths magnetic eld, and means for recording therelative positions of said elements.

8. Well surveying apparatus comprising a section of tubing to bepositioned in a Well, an instrument body to be lowered into the Well andinto said section of tubing, a pair of magnetic compass elements mountedto the body for rotation about a common vertical axis and having northand south magnetic poles in such proximate relation `8 polar relation inwhich the relative positions of the elements are reversed from their.positions assumed when subjected only to the earths magnetic eld.

9. Well surveying apparatus comprising a section of tubing to bepositioned in a well, an instrument housing to be lowered into the welland into said section of tubing, a pair of magnetic compass elementsmounted in the housing for rotation about a common vertical axis andhaving north and south magnetic poles in such proxi mate relation thatthe elements are mutually attractive, one of said elements beingmagnetized suiiiciently more strongly than the other that When subjectedto only the earths magnetic field said one element maintains the otherin a position substantially completely reversed from that of the oneelement and from the position which said other element would assume inthe absence of said mutua attraction, a magnetic insert in the wall ofsaid section of tubing of a strength sucient to attract the Compasses,when brought opposite the insert, in substantially corresponding polarrelation in. which the relative positions of the elements are reversedfrom their positions assumed when subjected only to the earths magneticfield, and means in said housing for recording the positions of saidelements.

JOHN C. HEWITT, JR.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 1,877,593 Roman Sept. 13, 1932 1,971,189 Leibing Aug. 21, 19342,120,570 Hyer June 14, 1938 2,123,045 Hoare July 5, 1938 2,169,342Hewitt 1 Aug. 15, 1939 2,187,367 Smith Jan. 16, 1940 2,319,212 CooleyMay 18, 1943 2,419,468 Smith Apr. 22, 1947 2,461,864 Zuschlag Feb, 15,1949 2,476,137 Doll July 12, 1949

